The size of mosaic blocks in lead powder was determined on the basis of the primary extinction effect of x rays. Integrated intensities of nine reflection lines in the Debye‐Scherrer spectrum with CuKα radiation were measured with a Geiger counter spectrometer. The mosaic size was calculated by comparing these values with theoretical values of the intensities. Correction for absorption of x rays in the specimen powder was especially important because of the large absorption coefficient of lead. The order of magnitude of the mosaic size was found to be 10−4 cm. From this value, the dislocation density was calculated to be of the order of 108 cm−2. The dislocation density decreased slightly when the specimen was annealedin vacuo at 150°C for a long time.

The current‐voltage characteristics of high‐pressure (0.25–300 mm) rare‐gas diodes have been measured. Data have been taken on diodes containing xenon, argon, and helium as the ambient gas, and tungsten,tantalum,rhenium, thoriated tungsten, and an oxide cathode as filamentary cathodes. Some unexpected phenomena have been observed and some of these general results can be summarized as: (1) The current vs voltage characteristics of argon‐ and xenon‐filled diodes, at gas pressure above 1 mm, do not obey any space‐charge law if the cathode temperature is above 2400°K. (2) The above violation of space‐charge relations in argon‐ and xenon‐filled diodes is found with tungsten,tantalum, or rhenium filaments, which can be operated above 2400°K. When thoriated tungsten or the oxide cathode, which operate below 2400°K, are used as filaments, the current‐voltage characteristics of the diode follow a space‐charge relation (current‐voltage characteristics independent of temperature). (3) The current vs voltage characteristics of helium‐filled diodes, however, do obey the space‐charge relations at all filament temperatures available with the present cathodematerials. (4) Some very unusual early breakdown phenomena (breakdown at potentials below ionization potential) were observed in these high‐pressure rare‐gas diodes employing a hot cathode. These data can be explained qualitatively by postulating the existence of thermally generated xenon or argon gas ions at temperatures in the range of 2400°K. An attempt will be made to justify this assumption by a semiquantitative theoretical treatment based on Saha's thermal ionization theory rather than the surface ionization theory of Langmuir and Kingdon.

A consideration of the crystal structures of simple binary compounds shows that they can be represented by closest packings of the larger anions in which two kinds of interstices are available for occupation by the metal atoms. In hexagonal closest packings, the octahedral voids form continuous chains by sharing opposite faces while the tetrahedral voids form isolated pairs. In cubic closest packings, each kind of void shares faces only with unlike voids. The specific diffusion paths available in these compounds depend, therefore, on the manner in which the voids are occupied. Continuous diffusion paths comprised of normally unoccupied voids exist in ZnO and α‐ZnS type structures so that voidal diffusion can take place without requiring defect formation. Similarly, voidal diffusion can occur in BiO3, CrCl3, and CdI2 type structures. Conversely, all possible continuous diffusion paths are blocked by metal atoms in the NiAs, NaCl, and antifluorite‐type structures so that vacancy or interstitialcy mechanisms are necessary to account for diffusion.

The effect of available diffusion paths on activation energies are considered for silver iodide, zinc oxide, and bismuth selenide. It is shown that the energy in β‐AgI should be nearly twice that in γ‐AgI because the Ag atoms in tetrahedral sites first must be displaced to octahedral voids before voidal diffusion can occur in the beta modification. The 2:1 ratio between the self‐diffusion energies of Zn determined by radioactive tracer and electrical conductivitymeasurements in ZnO is similarly explained. It is also shown that the difference between the activation energies for diffusion in BiSe and Bi2Se3 can be used to determine the formation energy of vacancies in BiSe. The agreement between these predictions and experimentally determined values attests that qualitatively accurate explanations can be based on considerations of the crystal structure.

Low‐resistivity n‐type GaAs crystals with silicon donors are compensated with diffused copper to produce high‐resistivity crystals in a manner which is amenable to semiquantitative description in terms of a simple thermodynamic model. The high‐resistivity GaAs:Cu crystals are subjected to photoelectronic analysis, including room temperature Hall and photo‐Hall measurements, to obtain information about the effects of deep‐lying imperfections on the properties of the initial n‐type GaAs. In addition to three deep donors previously reported, five acceptors are revealed. A 0.42‐ev acceptor level, when compensated, provides a long electron lifetime resulting in high n‐type photosensitivity at low temperatures. Evidence for effects on the electron mobility is obtained for compensated deep donor levels, important mainly in high‐resistivity n‐type material, and for compensated acceptors lying 0.22 ev above the valence band, important mainly at low temperatures.

A flash method of measuring the thermal diffusivity,heat capacity, and thermal conductivity is described for the first time. A high‐intensity short‐duration light pulse is absorbed in the front surface of a thermally insulated specimen a few millimeters thick coated with camphor black, and the resulting temperature history of the rear surface is measured by a thermocouple and recorded with an oscilloscope and camera. The thermal diffusivity is determined by the shape of the temperature versus time curve at the rear surface, the heat capacity by the maximum temperature indicated by the thermocouple, and the thermal conductivity by the product of the heat capacity,thermal diffusivity, and the density. These three thermal properties are determined for copper, silver, iron, nickel, aluminum, tin, zinc, and some alloys at 22°C and 135°C and compared with previously reported values.

The switching time and the coercive field in ferroelectric BaTiO3 are known to depend on crystal thickness. A model along the following lines is proposed to explain the experimental results: on the crystal surface there is a thin layer of electrically biased and mechanically strained BaTiO3 which has a much smaller dielectric constant than the bulk. It is proposed that the electrical bias and the mechanical strains in the surface are caused by a Schottky exhaustion layer. This model and the model proposed by Drougard and Landauer are discussed and their predictions are compared with experimental results.

The problem of determining the effective thermal conductivity of a two‐phase system, given the conductivities and volume fractions of the components, is examined. Equations are described which have been proposed as solutions to this problem, including those of Maxwell, de Vries, and Kunii and Smith, the weighted geometric mean equation, and an equation based on a three‐element resistor model found applicable to the analogous electrical conductivity problem. Experimental results are presented for five unconsolidated samples: three quartz sand packs, a glass bead pack, and a lead shot pack. The method of conductivity measurement using the transient line heat source (thermal conductivity probe) is described. Data are reported showing the variation of effective thermal conductivity with porosity, solid particle conductivity, saturating fluid conductivity, and the pressure of the saturating gas. From considerations based on the kinetic theory of gases, it is shown that the characteristic dimension of the pore space, with respect to heat conduction in the gas occupying this space, is smaller than the mean particle diameter by a factor of roughly 100. The thermal conductivityequations which best represent the observed data are those of de Vries, and Kunii and Smith, and a slightly modified version of the resistor model equation.

Measurements have been made of the effective thermal conductivity of porous sandstones. The method is based on the transient heating effect resulting from use of a line heat source. Data are presented for six sandstones ranging in porosity from 3 to 59% and show the variation of thermal conductivity with porosity, the conductivity of the saturating fluid, the pressure of the gas filling the pore space, and overburden pressure. The results are compared with those previously obtained for unconsolidated sands. All samples, except one, exhibited a lower thermal conductivity when saturated with a gas at atmospheric pressure than when saturated with a liquid of the same conductivity as the gas. An explanation for this effect, in terms of the kinetic theory of gases, is advanced and substantiated by other data. Finally, the validity of certain equations for the thermal conductivity of two‐phase systems is examined; the weighted geometric mean of the two constituent conductivities is found to agree well with the measured effective conductivities.

The ratio of the capture cross section of a sensitizing center for a photoexcited hole to the subsequent capture cross section for a free electron, in n‐type photoconductors, can be determined from the measurement of the thermal quenching of photoconductivity as a function of excitation intensity. The magnitude of the ratio gives information about the charged state of the sensitizing center. A summary of many such measurements on seven different photoconductors of type II–VI or III–V supports the hypothesis that doubly charged sensitizing centers are present in some of these materials, but that singly charged sensitizing centers are present in the majority.

The variation of 1/fnoise in thin, single crystalgermanium filaments was investigated by using gaseous ambients to change the surface potential of the sample. The noise samples, having a thickness of only 4 μ, were extremely sensitive to variations in the surface potential and exhibited large fractional changes of the total sample conductance as a result of the surface conductance fluctuations which were interpreted as the 1/fnoise. These experimental results showed a definite noise minimum when the sample surface potential corresponded to the sample conductance minimum. The rms conductance fluctuation varied roughly linearly with ΔG, where ΔG is the increase of the sample conductance with respect to the minimum value. The slope of the curve for the condition of an accumulation layer on the sample surface was an order of magnitude less than that for the inversion layer. The amplitude of the accumulation noise agreed (within a factor of two) with the prediction of McWhorter's majority carrier trapping effect, but the inversion noise was an order of magnitude greater.

Field configuration and resonant frequency are determined for the lowest azimuthally‐independent mode of a coaxial cavity surrounding a circular tube, Several values of the width of the coupling gap are considered, and the central problem consists in determining the tangential electric fieldEt in that gap. It was found that the fields near the axis of the accelerator are quite insensitive to the actual profile of Et, and that satisfactory results are obtained by assuming Et to be constant. The problem is repeated for a parallel plane configuration, with the purpose of investigating the influence of the flattening of the cavity. Computations show that the two configurations yield fairly similar results.

The previously reported three‐parameter stress function has been applied to natural rubbers similar to those used for engineering purposes. These rubbers were selected to cover a harness range from 30 to 80 British Standard Degrees. A suitable choice of values for the parameters A, B, and β was found to give a good description of the stress‐strain characteristics in pure shear, and positive and negative stretch squeeze. This agreement applied up to the maximum possible strains. Unique functional relationships were found to exist between the three parameters and rubberhardness. Theoretically, it would be possible to reduce the three‐parameter stress function to a single‐parameter stress function. As previously reported, this confirms and hence is indirectly confirmed by Blackwell's results [Trans. I. R. I. 28, 75 (1952)].

A model and resulting theory for the exoemission of electrons from metal surfaces are presented. The model states that the exoemission is governed by the diffusion of vacancies in the metal, vacancies created by the abrasion. A vacancy, upon diffusing to the surface, may give up its energy to an electron. However, when in the same event, a photon also transfers its energy to the electron, the electron may be emitted. Experiments performed show the exoemission decay to be composed of two exponential decays. Both exponential decay constants vary with temperature according to the equation:.Here, F is a constant and E is an activation energy which, measured, approximates 5.6 kcal/mole. A comparison between experiment and theory give the theory corroboration.

The effect of hydrostaticpressure on the energy gap of Bi2Te3 has been investigated in the pressure range one to 30 000 atm. From resistivity measurements as a function of temperature and pressure, it has been determined that the energy gap decreases from 0.171 ev at one atmosphere to 0.104 ev at 30 000 atm, corresponding to ∂Eg(0)/∂p=−2×10−6 ev/atm.

The pairwise coupling of modes in distributed systems such as the traveling‐wave parametric electron‐beam amplifier and many other types is shown to permit only two types of interaction. One type, called β coupling, results in the periodic interchange of the signal between the modes, as typified in the Kompfner‐null coupler. The other, γ coupling, results in the exponential growth of the mode, as in the TWT and in the pump section of a parametric amplifier. The nature of the resultant interaction is a direct consequence of the underlying relations contained in the conservation law that applies throughout the system, i.e., in the separate parts of the system and that is independent of the various coupling coefficients. The ``rank'' and ``signature'' of the metric that expresses this conservation law is sufficient to determine the type of behavior. The direction of flow of energy in the coupled modes imposes a duality on these relations. Where modes of opposite directionality are coupled, β coupling causes system amplification, while γ coupling causes system interchange. These relations are generalizations of effects that have been studied in detail for many specific systems. They are not, however, consequences of the details of the system but are, rather, the only alternatives possible under assumptions that are broad in scope and generally applicable to devices of interest.

Thermorheological simplicity is available for the extrusionflow curves of polymers in a way similar to the case of creep or stress relaxation. The true consistency curves for acrylic resin which were obtained from the extrusionflow curves at various extrusion temperatures by the help of the end‐correction factor ξ are superimposed by shifting along the log Dw′ (where Dw′ is apparent maximum shear rate at the die wall). Thus the consistency curves by extrusion which are useful for evaluating the viscoelastic behavior of amorphous linear polymers can easily be determined over a sufficiently wide range of shear rates by the change of extrusion temperature.

Electron‐transparent dislocation‐free platelets of cadmium were deformed in tension parallel to the basal plane, inside an electron microscope, in the temperature range from +25° to −150°C. At high strain rates the crystals twinned. At low strain rates (≲10−2 sec−1) the glide system depended on α, the angle between the tensile axis and a close‐packing direction. For 0≤α≲20° pyramidal glide on the (112̄2) [1̄1̄23] system occurred. For 20°≲α≤30° a new glide system, (101̄1) [12̄10], was identified which has not yet been observed in large cadmium crystals. Edge dislocations with a ⅓[12̄10] Burgers vector moved across the entire crystal on (101̄1) planes without multiplying or forming obstacles to further glide. Occasionally, at high strain, fracture occurred on a (101̄1) plane. The observations suggested that, in the temperature range studied, the flow stress for (101̄1) [12̄10] glide was considerably lower than that for prismatic glide on the (101̄0) [12̄10] system, slightly higher than that for (112̄2) [1̄1̄23] glide, and independent of strain for a given temperature.

The (112̄2) [1̄1̄23] glide system was studied in thin, dislocation‐free cadmium platelets by transmission electron microscopy and compared with observations on zinc platelets. Screw dislocations with a ⅓<1̄1̄23> Burgers vector were formed at the edges of the crystal and moved primarily on {112̄2} planes. Elongated, sessile dislocation loops were formed on basal planes when screws developed large jogs during cross‐glide. Smaller numbers of secondary ⅓<1̄1̄20> dislocations were also formed and moved on basal planes. Observations in the temperature range −150° to +25°C showed that the behavior of the long loops and of the other dislocations in cadmium and zinc varied with temperature as follows: (1) At temperatures lower than ∼−120° in Cd and ∼−80° in Zn, the long loops were stable and practically no recovery took place. High densities of loops and networks of secondary dislocations were built up and hardened the crystal. (2) In the intermediate temperature range −120° to −40° for Cd and −80° to +10° for Zn, the long loops split up into rows of circular loops, which were then stable. The process involved the pipe‐diffusion of material around the long loops and required a lower activation energy than that for climb. Some of the circular loops were found to contain stacking faults. (3) At high temperature, above ∼−40° for Cd and ∼+10° for Zn, circular loops annealed out by climb with an activation energy ∼0.8 ev for Cd and ∼0.95 ev for Zn; secondary dislocation networks dispersed by climb; and the dislocation density, and therefore the work‐hardening, was small.

At high beam intensities dislocation loops often grew by climb, probably as a result of the formation of point defects by ion bombardment, the ions being formed by the interaction between electrons and residual gas molecules.

Surface waves are defined as waves exponentially decreasing on both sides of a plane interface. It is shown how all such waves can be generated from a single Hertz vector perpendicular to the interface. The relations between the propagation parameters of the waves and the material constants are derived in a general case which includes media with different magnetic permeabilities. The condition for the existence of surface waves is derived.